This invention relates to the field of medical equipment and in particular it is concerned with medical catheters and cannulae. An improved coupling device for connecting a cannula or catheter to a connection tube through which liquid to be administered to a patent is delivered, or fluid taken from a patient is collected, is described in my International Patent Application No. WO 98/02206. The invention described herein concerns modifications and further improvements to the coupling device described i the aforesaid application No. WO 98/02206.
Whereas the coupling device specifically described in WO 98/02206 has an internally splined sleeve carried by a male member of the device, and an externally splined collar is slidable on the female member for engaging and disengaging the splined sleeve to lock and unlock a cap which is rotatable to secure the male and female members in coupled cooperation, according to the modified construction of the invention described herein, external keying means such as splines are provided on the male member and the female member has a slidable part with complementary keying means on an inner surface. The keying means can conveniently be provided on the cap which forms part of the male member, and in the presently preferred embodiment, the cap is formed with a series of splines uniformly spaced around its exterior peripheral surface. An advantage of this construction is that the form of the male member is such that in visual appearance it may differ only very slightly, as a consequence of the provision of the splines, from male coupling members which have been in use on administration sets for a number of years and with which medical staff feel comfortable and are familiar. In the preferred embodiment the slide on the female member includes a collar with an extension sleeve having on its inner peripheral surface a series of splines complementary in arrangement and configuration to the splines of the cap.
Some catheters and cannulae of different kinds in use today and intended for different specific applications, such venous catheters, spinal catheters, nasal catheters, etc, are equipped with female coupling members adapted to fit with the identical forms of male coupling member with which the different types of administration sets intended for use with the respective catheters are supplied. As a result it is not impossible for a wrong administration set to be operatively connected to a catheter, especially if a patient is fitted with a number of catheters, and the consequences of such a mistake can be very serious and could even be fatal to the patient. The invention addresses this problem and as a solution it proposes a group or range of couplings for use with respective catheters adapted for different application to a patient, each coupling including a female member with a socket, a male member having a spigot for push fit engagement in the socket, a cap provided on one member and rotationally engageable with the other member to secure the spigot against disengagement from the socket, and a locking arrangement to lock the cap against rotation in the disengagement direction, e.g. as incorporated in the coupling devices according to WO 98/02206 and according to the present application, wherein each coupling of the group or range has complementary engaging means on the male and female members adapted to prevent the male or female member being operatively connected to a female or male member, respectively, of another coupling in the group or range.
Most conveniently, the complementary engaging means are provided by the locking arrangements and in the preferred form of coupling as described in detail herein the pattern of splines on the cap and within the sleeve is unique to each kind of catheter and associated administration set, so that any attempt to make an incorrect connection between an administration set and a catheter will be thwarted.